# How do you calculate (7.2 times10^-2)(1.8 times 10^-4)?

Jul 1, 2016

$1.296 \times {10}^{-} 5$

#### Explanation:

To multiply $4 {x}^{-} 5 \times 7 {x}^{-} 8$

Multiply the numbers and add the indices because both bases are $x$

$4 {x}^{-} 5 \times 7 {x}^{-} 8 = 28 {x}^{-} 13$

Do exactly the same with $\left(7.2 \times {10}^{-} 2\right) \times \left(1.8 \times {10}^{-} 4\right)$

$\left(7.2 \times 1.8\right) \times \left({10}^{-} 2 \times {10}^{-} 4\right)$

=$12.96 \times {10}^{-} 6$

However this is not in standard form because the first number is more than 10.
The answer has to be adjusted by moving the point to the left and increasing the power by 1. $\text{ } \left(12.96 = 1.296 \times {10}^{1}\right)$

$12.96 \times {10}^{-} 6$

$1.296 \times {10}^{-} 5$